The manufacture of high intensity discharge lamps, for example, metal halide lamps and high-pressure sodium lamps, involves the frit sealing of metal leads to the ceramic envelopes. For high-pressure sodium lamps, a glass-ceramic system of Al2O3—CaO—BaO—MgO—B2O3 has been employed to effect the seal between the metal lead, usually niobium, and the ceramic envelope, usually, polycrystalline alumina (PCA). In metal halide lamps, because the halide fill will attack niobium, it has been customary to lower the niobium-to-PCA seal temperature to a level where the kinetics is sufficiently slow to allow reasonable life and further, to use a halide-resistant frit seal of Dy2O3—Al2O3—SiO2 frit plus a molybdenum-welded-to-niobium lead structure.
While all of these solutions have provided some benefit, it would be an advance in the art to provide an improved brazing alloy.